This invention relates to photonic modules that have the ability to add and drop specific information-carrying wavelengths propagating within a fiber optic network, hereinafter referred to as optical add/drop multiplexers (OADM).
Optical add/drop multiplexers (OADM) have the ability to add and drop specific information-carrying wavelengths propagating within a fiber optic network. A block diagram illustrating how an OADM 1 functions to add wavelengths xcexxe2x80x2i . . . xcexxe2x80x2j . . . xcexxe2x80x2k and drop wavelengths xcexxe2x80x2i . . . xcexxe2x80x2j . . . xcexxe2x80x2k from an input xcex1-xcexN is shown in FIG. 1.
A widely discussed architecture for OADMs involves using arrayed waveguide grating (AWG) routers and 2xc3x972 optical switches. This architecture is schematically shown in FIG. 2. Here, AWGs 12 are used as multiplexers/demultiplexers and switches 14 are used for selecting the channels to be added and dropped. This architecture can be made with commercially available, stand-alone components (e.g., a fiber pigtailed AWG that is then connected to fiber pigtailed switches by fusion splicing and connector attachment). AWGs are produced commercially by, for example, Hitachi, Lucent, Nortel, SDL, and JDS Uniphase. 2xc3x972 switches, in both opto-mechanical and thermo-optical varieties, are produced commercially by vendors such as JDS Uniphase, Fitel, Dicon, and Corning.
Unfortunately, the architecture illustrated in FIG. 2 has a number of shortcomings. This architecture is difficult to assemble due to the number of fiber connections, and is expensive. In addition, this architecture suffers from a high insertion loss. Furthermore, this architecture scales very poorly as the number of wavelengths is increased. Metropolitan area network applications, for example, may demand that 32, 64 or 80 wavelengths be added or dropped in a given OADM.
To solve these problems, attempts have been made in the prior art to integrate the filtering function of AWGs and the switching function of switches on a single substrate. One such attempt, using a planar glass technology, is described by K. Okamoto et al. in their paper entitled, xe2x80x9c16-Channel Optical Add/Drop Multiplexer Consisting of Arrayed Waveguide Gratings and Double Gate Switches,xe2x80x9d Electronic Letters 32, 1471 (1996). Here, several AWGs were made in planar glass (silica on silicon) on the same substrate, and Mach-Zehnder-based thermo-optic switches were integrated on the same substrate. Unfortunately, there are several disadvantages to this approach. Mach-Zehnder-based switches require a large amount of area on the chip. In addition, Mach-Zehnder-based switches are very sensitive to fabrication errors and suffer from poor isolation.
Another attempt toward an integrated OADM has been described by Giles et al. in their paper entitled, xe2x80x9cReconfigurable 16-Channel WDM Drop Module Using Silicon MEMS Optical Switches,xe2x80x9d IEEE Photonics Tech. Lett. 11, 63 (1999). Here, AWGs are fiber-coupled to an array of MEMS-type switches. Unfortunately, this approach is not fully integrated and is not solid-state.
Clearly, there is a need for a solid-state OADM that is fully integrated on a single substrate and not sensitive to fabrication errors. Ideally, the switches used in such an OADM should not require large areas on the chip and should further have good isolation characteristics.
The present invention provides an integrated, high performance optical add/drop multiplexer (OADM) comprising a multilayer stack whose function is to add or drop specific information-carrying wavelengths propagating within a fiber optic communication network. The stack structure eliminates or at least ameliorates the shortcomings associated with the prior art. The stack comprises a first layer comprising a silicon or silica substrate, a second layer comprising an undercladding layer, a third layer comprising a core glass layer, and a fourth layer comprising an overcladding layer. In another embodiment, the stack comprises a first layer comprising a silicon or silica substrate, a second layer comprising an undercladding layer, a third layer comprising a polymer layer, a fourth layer comprising a core glass layer, and a fifth layer comprising an overcladding layer.
The invention also provides an integrated optical add/drop multiplexer (OADM) comprising a substrate, an undercladding layer disposed on the substrate, a core glass layer disposed on a portion of the undercladding layer, and an overcladding layer disposed on the undercladding layer and the core glass layer. The core glass layer includes an arrayed waveguide grating (AWG) and the overcladding layer comprises a polymer and includes an optical switch.
The invention also provides an integrated optical add/drop multiplexer (OADM) comprising a substrate, an undercladding layer disposed on the substrate, a core glass layer disposed on a portion of the undercladding layer, a polymer layer disposed on the undercladding layer adjacent the core glass layer, and an overcladding layer disposed on the polymer layer and the core glass layer. The core glass layer includes an arrayed waveguide grating (AWG) and the polymer layer includes an optical switch.